Don't worry. It seems to be standard for BE pax these days. You'll appear on the "Standby/Seat Request" list but rest assured you're confirmed. The only problem is Amex Centurion Lounge doesn't like these no-seat boarding passes but you may be able to ask the GA or check-in agent to assign you one on a good day. I've always walked up to the podium when the GA arrived and asked for a seat - generally the GA just gives me a C+ seat or a preferred seat if the flight is reasonably empty, even when flying BE.